May 2013 - Boost - lists.preview.boost.org

[wave] trace doesn't output errors.
by Adrian_H 07 May '13

07 May '13

I've got a really annoying and difficult to track down PP error. I'm attempting to use wave to see the expansion, but it is slow going. The output is correct, in both the g++ PP and the wave parser. g++ states: *error: macro "BOOST_PP_SEQ_ELEM_III" requires 2 arguments, but only 1 given*, wave states *warning: too few macro arguments: BOOST_PP_SEQ_ELEM_III*, but when I try using the tracer it doesn't say when this occurs. Is it possible to turn this on? Or is there no 'on' and I have to go into the wave code and code it on? If the latter, where would I do this? Thanks, Adrian -- View this message in context: http://boost.2283326.n4.nabble.com/boost-wave-trace-doesn-t-output-errors-t… Sent from the Boost - Dev mailing list archive at Nabble.com.

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Git Modularization Ready for Review
by Niall Douglas 07 May '13

07 May '13

> After substantial work, including massive changes by me and Daniel Pfeifer to > KDE's svn->Git conversion tool, we have captured every Boost SVN commit in a > Git repository. You can view the results at > > http://github.com/boostorg > http://bitbucket.org/boostorg > > Daniel and I are ready to accept your feedback on the results of modularization, > and especially your pull requests containing edits to the ruleset. I will the > steering committee to establish a formal review period, though. I'm a bit confused. This looks like a hand written map of parts of Boost SVN onto multiple GIT repos. Am I understanding correctly? I'm far more confused as to why? Surely the conventional approach is to convert a SVN repo to GIT. Then people hive off their particular bits into submodules as and when they themselves decide and they are ready. It looks here that Boost has decided on skipping the intermediate stage and going straight to submodules. That sounds awfully fraught: it also demands a lot from those library maintainers not familiar with Git. Submodules are extremely different to SVN externals - they're a very light link, and in many occasions Git does not auto-update submodules even when you tell it (i.e. it'll fetch, but silently not checkout head if it thinks you might lose data). Also, how is Boost going to manage dependency breakage across multiple submodules? Are you planning to keep headers in one monolithic repo but keep anything resulting in a DLL/SO in a submodule? Or are you planning to break out the headers into submodules too? I can see it becoming quite easy for submodules or branches or forks thereof to get out of step with one another. I can see the present submodule heavy approach introducing a lot of anti-Git workflow because those submodules inside the boostorg organization are treated as special compared to other submodules. I'm confused. Sorry. I'm probably not making any sense. Is there a design rationale document somewhere? I can't see one up to date on Google. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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Re: [boost] Live read-only GIT mirrors of Boost trunk SVN
by Niall Douglas 07 May '13

07 May '13

> > All branches and tags, as far as I can tell, are mirrored correctly. I've > > set a cron job every 24 hours. Theoretically if we had an authors mapping > > file it would work in the opposite direction too i.e. be read-write. > > Nice. You can find a complete author mapping here: > https://github.com/ryppl/Boost2Git/blob/master/authors.txt Arse. I only rebuilt the mirror this weekend because it wasn't mirroring tags/release/* which has obvious value. Fixed now. > > My next task is to live mirror a github repo into Boost Sandbox. Currently > > SubGit segfaults on this due to the complex SVN properties auto-translation > > which requires a specially marked up .gitattributes, but the author is very > > keen to fix the problem. In theory then it ought to just work. > > > > Any mistakes in my Boost mirror, or any problems, or even thoughts are > > gratefully received. > > Don't put too much effort into this; Boost SVN->Git modularization is > just about ready for review :-) My experience with SubGit has been very, very good. I would *strongly* recommend it over git2svn. The company which develops it has been very impressive in response rate and going the extra mile to help me figure out problems. BTW Dave with much help from the same company I've figured out the opposite flow: automated Git => Boost SVN. It took a lot of trial and error to work around Boost's MIME type and EOL conventions, but you can see an exact automated mirror of https://github.com/ned14/TripleGit at http://svn.boost.org/svn/boost/sandbox/triplegit/. I had to squash history because of the MIME type problems though :( but from now on it should be live. I think it would be quite easy to set up a live perfect Git mirror of all Boost SVN, do a transition period where SVN is writeable but GIT read only, and then one day the switch is flipped and it goes the other way round. That way anyone dependent on SVN keeps on working, but without write access. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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[chrono/date] Unit specifiers arithmetic
by Vicente J. Botet Escriba 07 May '13

07 May '13

Hi, Moving from checked dates to unchecked ones by default and forcing to user the Unit specifiers year/month/day in any date constructor (even the unchecked ones) has some ugly consequences. Note that I was able to build an unchecked date as date d(2013,5,6, no_check); Given year y; month m; day d; the following will not compile now as the constructors expects a year but y+1 is an int. date d(y+1, m, d); The user needs to type date d(year(y+1), m, d); Is this what we want to provide to the user or should we add basic arithmetic on these unit specifiers? Best, Vicente

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Re: [boost] [gsoc-2013] Boost.Thread/ThreadPool project
by Niall Douglas 07 May '13

07 May '13

> Le 30/04/13 17:16, Niall Douglas a ?crit : > >> Le 29/04/13 21:35, Niall Douglas a ?crit : > >> Could you explain me what a central asynchronous dispatcher is? > > An asynchronous procedure call implementation. Here's Microsoft's: > > http://msdn.microsoft.com/en- > us/library/windows/desktop/ms681951(v=vs.85).as > > px. Here's QNX's: > http://www.qnx.com/developers/articles/article_870_1.html. > > Boost.ASIO is the same thing for Boost and C++ but implemented by > > application code. It is *not* like asynchronous POSIX signals which are a > > nearly useless subset of APCs. > I don't see the term "central asynchronous dispatcher" used in any of > the links. Could you clarify what it is? I have to admit I'm struggling to see where your block is, but Dave Abrahams often found the same with me, so it must be me. A central asynchronous dispatcher is the loop which sends callbacks/events to be invoked/processed by other execution contexts. Every OS has at least one in the kernel. Most GUI toolkits like Qt have one. Boost has at least one in the form of Boost.ASIO. The central means one execution context does the dispatch. The asynchronous means that callbacks are processed by recipients asynchronous to the dispatcher. And dispatcher, well that dispatches. > >> If not, please could you elaborate what kind of optimizations can be > >> obtained? > > If you have transactional memory in particular, you gain multi-CAS and the > > ability to (un)lock large ranges of CAS locks atomically, and a central > > dispatcher design can create batch lists of threading primitive operations > > and execute the batch at once as a transaction. Without TM, you really need > > the kernel to provide a batch syscall for threading primitives to see large > > performance gains. > I'm really lost. Multi-word Compare-And-Swap (MCAS) is one of the biggest gains from Transactional Memory. Indeed WG21 has SG5 dedicated to integrating TM into C++17. Some models of Intel's Haswell come with hardware TM assist. I'd take a reasonable guess that MCAS will benefit centralized kernel-based threading primitives architectures such as Windows NT more than decentralized threading primitive architectures such as POSIX. That said, I could see Linux using TM for batch multi-kernel-futex ops, though I'd have to say implementing that without breakage would be daunting. Either way, a central asynchronous dispatcher has information a decentralized implementation does not. That opens more scope for optimization. > > Boost.ASIO's core is boost::asio::io_service. That is its dispatcher > > implementation which each dispatch execution context being executed via > > boost::asio::io_service::run() which is effectively an event loop. Third > > parties then enqueue items to be dispatched using > > boost::asio::io_service::post(). You don't have to run Boost.ASIO using > > multiple threads: it can be single threaded. > > I could not comment until I understand what Boost.ASIO provides and it > can interact with thread_pools :( Boost.ASIO provides a per-thread capable event loop implementation. That automatically makes it an example of a thread pool manager. You may find N3562 Executors and schedulers coproposed March 2013 for Bristol by Google and Microsoft of use to you in understanding the relation between thread pools and Boost.ASIO (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3562.pdf) My proposed Boost.AFIO library is an implementation of that same N3562 idea, albeit I extend Boost.ASIO which is IMHO more C++-y whereas Google and Microsoft have gone with proprietary implementations. Also, they include timing and many other more general purpose features, and mine does not (currently) as it's mainly aimed at maximising input/ouput with highly jittery random latency storage. Niall --- Opinions expressed here are my own and do not necessarily represent those of BlackBerry Inc.

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[heap] van Emde Boas tree
by Jeremy Murphy 07 May '13

07 May '13

Should I contact Tim Blechmann directly about the idea of adding a van Emde Boas tree to Boost.Heap, or is proposing it here the appropriate way to go about it? Thanks, cheers. Jeremy

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[any] Divergence between Boost.Any and standard library proposal
by Beman Dawes 07 May '13

07 May '13

A fresh draft of the proposal is up at http://beman.github.com/dot16/any-proposal.html In testing new any_cast examples, Boost.Any is handling one case differently from the proposal: any x; ... x = "Meow"; // x holds const char* This works fine with the Adobe implementation, but with the Boost implementation g++ 4.7.0 -std=c++11 reports: In file included from any_cast_test.cpp:5:0: c:\boost\trunk/boost/any.hpp: In instantiation of 'boost::any::holder<ValueType>::holder(c onst ValueType&) [with ValueType = char [5]]': c:\boost\trunk/boost/any.hpp:52:49: required from 'boost::any::any(const ValueType&) [wi th ValueType = char [5]]' c:\boost\trunk/boost/any.hpp:124:13: required from 'boost::any& boost::any::operator=(Va lueType&&) [with ValueType = const char (&)[5]; boost::any = boost::any]' any_cast_test.cpp:79:7: required from here c:\boost\trunk/boost/any.hpp:169:27: error: array used as initializer VC++ 2012 gets the same error, albeit with a much longer set of messages. AFAICS, the Adobe (and the proposed standard) behavior is preferred. The type does need to decay. Comments? --Beman

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[chrono/date] date conversion and arithmetic with unvalidated dates
by Vicente J. Botet Escriba 07 May '13

07 May '13

Hi, Note that N3344 suggest only day arithmetic for a day representation (which is always valid) and suggest only only a date representation. Could we apply arithmetic operations on a unvalidated date (without striving on UB)? e.g. day arithmetic on a ymd_date ymd_date d1(year(2013), may, day(66)); ymd_date d2 = d1 + day(1); If defined, which must be the value of d2? Could we convert a date representation to another one if the source date is unvalidated (without striving on UB)? e.g. ymd_date -> days_date ymd_date d1(year(2013), may, day(66)); days_date d2 = d1; If defined, which must be the value of d2? Best, Vicente

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[chrono/date] validated versus valid dates
by Vicente J. Botet Escriba 07 May '13

07 May '13

Hi, Allowing to build dates that are not validated doesn't mean that they are not valid. A validated date is always valid. E.g date d(year(2013), may, day(5)); d is not a validated date but is valid. Having a is_validated() function in addition to is_valid() could have its uses assert( ! d.is_validated() && d.is_valid() ); is_validated() function forces to use a bit to store this information on the date representation, but it improves the performances of the is_valid() function. Moving from a possible unvalidated to a validated one would need date d1; ... date d2(d1.year(), d1.month(), d1.day(), check); Instead of this a validate factory makes this clearer date d1; ... date d2 = validate(d1); date validate(date const& dt) { if (dt.is_validated()) return *this; else if (dt.is_valid()) { date res(dt); res.set_validated_(); // this is private return res; } throw bad_date(); } Best, Vicente

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Am I missing something or is Boost: String dictionary?
by david.hagood＠gmail.com 06 May '13

06 May '13

One of the libraries I work with (libXML2) has a very useful concept called a string dictionary, and I am surprised this doesn't appear to be in either STL or Boost. Am I missing something, or is Boost missing something? The basic idea is: Given you have a string and an instance of a dictionary, you can: 1) check if the string is already in the dictionary. 2) Add the string to the dictionary and return the dictionary entry (if the string is already present, return existing entry). The dictionary entries contain a copy of the string. Entries may be compared for equality/inequality in O(1) time. The lifespan of the strings in the entry is managed by the entry. This really simplifies writing parsers and the like, and is such a useful concept that I'm really surprised not to see it in STL or Boost.

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